Heaters are used in many applications where heat is required to help warm an adjacent area. Electrothermal heating is a common way to warm surfaces and spaces on an aircraft by providing heaters bonded to or integrated within the structure. It may also be used in internal areas of an aircraft, examples in areas such as the cockpit cabin or floors for warming, pipes that may contain liquids that could freeze, and even for volumetric heating of a passenger or air cargo compartment. In electrothermal heating systems, heat energy is typically applied through a metallic heating element via electrical power supplied by aircraft or appropriate application generators. Typical heating elements are made from foil, wire and metallic-coated fabrics.
Generally, the heating element of an electrothermal heater should be highly flexible to conform to many types of surface areas and shapes to be protected. Such surface areas may be either two- or three-dimensional. In addition, such heating elements should also withstand fatigue and foreign object damage (FOD) requirements for each particular application. Further, such heating elements should be capable of being specifically designed to provide exact power levels (heat) and uniform heat distribution to the warmed surfaces or regions.
Most current heater elements are made from a single channel foil or wire element assembly 100, 200, respectively, as exemplified by the illustrations of FIGS. 1 and 2, respectively. Accordingly, a failure or break of the single element via FOD/fatigue in most current heater elements can reduce or eliminate the heating element's usefulness. The prior art also includes a movable sheet having a rectangular array of perforations and mounted on rollers, as disclosed in U.S. Pat. No. 5,590,854; a grid-type of electrical heating element that is painted on, as disclosed in U.S. Pat. No. 6,027,075, and a mesh of interwoven wire, as disclosed in U.S. Pat. No. 6,832,742.